Some clocks display the time in multiple cities or countries simultaneously. Such clocks typically indicate time in hours minutes and seconds, and may have multiple digital or analog displays, each display indicating the time in a different geographical area. Other clocks may incorporate a geographical display on the clock and provide a pointer which indicates the time in various geographical locations.
Although it is beneficial to know the time in hours, minutes and seconds, it is also beneficial to know whether it is day or night in a given geographical area. The ability to indicate the seasonal changes in day and night in a geographical location may be very useful. For example, it is important to know seasonal variations of day and night to understand agricultural growing and dormant cycles and to understand cultural customs which are based on seasonal fluctuations in day and night.
Time displayed in hours does not distinguish between day and night. Some clocks provide a shaded portion on the face of the clock. Night is indicated when the time pointer sweeps through the shaded portion of the clock face. Day is indicated when the time indicator sweeps through the portion of the clock face that is not shaded.
These types of day and night indications may be moderately accurate for geographical areas which do not experience very distinguishable shifts in day or night during seasonal variations, such as geographical locations situated near the equator. However, most locations in the world experience great fluctuations in the relative amounts of day and night depending on variations in seasons. This is especially true in geographic areas located in the extreme north and south. These areas experience weeks or months of continuous day or night. Therefore, it is difficult to indicate the relative amounts of day and night in these extreme locations based on a stationary shaded portion of a clock.
The relationship between the earth's rotation, time and seasonal variations in day and night can be a difficult concept to grasp. A device which demonstrates the seasonal variations in various geographical regions in respect to time and the earth's rotation could facilitate understanding of this concept.
What is needed is a time indicating device which indicates the time in multiple geographic locations and overcomes the problem of indicating the relative amount of day and night according to seasonal variations.